This invention pertains to an improved coal hydrogenation process for producing hydrocarbon liquid and gas products, wherein a coal-oil slurry is fed directly into a catalytic reaction zone with only minimal controlled preheating to provide improved hydroconversion and produce increased yields of light hydrocarbon liquid products and gas.
Conventional processes for coal liquefaction and hydrogenation include a preheating or thermal treatment step for the coal-oil slurry feed prior to the catalytic reaction step, as generally disclosed in U.S. Pat. Nos. 3,519,555; 3,700,584; 3,791,957 and 4,111,788. Other coal hydrogenation processes use fine recycled catalysts at plug flow conditions and low solvent/coal ratios, such as U.S. Pat. Nos. 4,090,943 and 4,102,775. In these processes, the coal-oil slurry feed is preheated to near the reactor temperature before feeding it into the catalytic reaction zone.
In these conventional coal hydrogenation processes utilizing a coal-oil slurry preheating step, the hydrogen donor potential or free radical concentration in the coal-derived slurrying oil is limited as is its mobility and the hydrogen therein is usually consumed during the coal preheating step. This lack of hydrogen donor materials in the coal-oil slurry during the preheating step causes undesirable recondensation materials such as asphaltenes and other unreactive high molecular weight materials to form, thereby increasing the yield of undesired heavy hydrocarbon liquids and reducing the yield of the more desirable light hydrocarbon liquid products. However, it has been unexpectedly found that by rapid exposure of the coal feed to the dilute solids high hydrogen content liquid and catalyst in the reactor after only a controlled minimal preheating, rapid hydroconversion of the coal to produce increased yields of lower boiling hydrocarbon liquid products is substantially enhanced.